The invention relates generally to the area of machine controls; and specifically, the invention provides a logic processor in combination with asynchronously operating modular data processors. This multiprocessor combination may be used to control the cycle of operation of a machine.
Traditionally, relay circuits have been used to control output devices, e.g. motor starters, timers, lights, control valves, solenoids, displays, etc., in response to the condition of input circuits,, e.g. limit switches, pressure and temperature transducers, push buttons, etc. The output devices govern the operation of the machine in accordance with a logical pattern of conditions of the input devices monitoring the machine operation. The relay logic circuits are wired together to duplicate the desired logical pattern such that the circuits operate to control the output devices in a predetermined manner as a function of the condition of the input devices. The relay logic circuits require a mechanical operation to perform their switching operation; and therefore, the circuits are inherently less reliable than solid state electronic switching devices. Further, the relay circuits become expensive as the complexity of the machine control increases. Finally, relay circuits are rigid in their architecture and hence are limited in their versatility and expandability.
In the last five years, a number of logic processors have become available which replace the relay logic circuits for controlling machines. Some of the logic processors are very simple in their construction and only capable of duplicating the relatively simple logic decisions executed by the relay logic circuits. However, other controllers include full computer capabilities and perform the full range of arithmetic operations available in a computer as well as the standard logic decisions. A review of the prior art reveals that there is a full range of processor designs and programming techniques. However, the prior art devices have one thing in common, they are all single processing units. This is satisfactory in units only having logic decision making capabilities; however, when arithmetic operations are required in addition to the logic decisions, the processor becomes very complex and expensive.
The disclosed invention proposes to overcome the deficiencies of the prior art systems by providing a modular and expandable multiprocessing system having a logic processor for governing the cycle of operation of a machine in accordance with a programmed set of logic instructions. The system includes one or more independent data processors operating asynchronously with the logic processor for executing programmed sequences of arithmetic operations selected by the logic processor.